1. Field of the Invention
The invention is related to readily changeable labelling systems wherein indicia bearing labels can be readily erased and changed. The invention is more specifically directed to a label utilizing a "magic slate" to provide the indicia bearing portion of the label. However an alternate embodiment is disclosed utilizing a protected easily erasable surface.
2. Description of the Prior Art
Presently most articles are labelled with fixed or relatively unchangeable labels. In some applications however a changeable label is desirable, in that the contents of the article or the status of the article has changed. One application in which this invention provides particular usefulness is providing a changeable label for video or audio cassettes, or cassette holders.
Video or audio cassettes can be used over and over to tape various events and programs, and as such, a changeable labelling system is very important to the user so that he or she can identify the program now recorded on the cassette. At the present time most users use adhesive paper strips that are secured to the cassette or holder. The location and identification of the program on the cassette is written on the strip so that a user may readily identify the contents of the cassette. When the tape is erased and another program recorded on the cassette the original indica on the tape must be crossed out, erased or another paper strip applied to the cassette holder. The present invention simplifies the changing of identifying indicia on articles such as cassettes or cassette holders.
Reusable erasable memo pads have been widely known and are primarily used in toys and novelties. Such pads are called "magic slates" and generally comprise a clay, putty or wax impression surface which is impregnated with an oil and is overlayed with a translucent sheet, see U.S. Pat. No. 1,455,579. A pointed instrument similar to a pencil is used to apply pressure to the translucent sheet and the sheet adheres to the impression surface creating a visible mark on the translucent sheet. The mark can be erased by lifting the translucent sheet away from the impression surface thereby breaking the adhesion and erasing the sheet.
Although "magic slates" have been principally used in toys, other more utilitarian uses have been considered. Generally, these uses have been directed to memo pads and record books wherein temporary notations must be jotted down, see U.S. Pat. Nos. 2,198,095, 2,663,095, 2,997,884 and 3,579,871. "Magic slates" have been used in switchboard message pads, wherein a single impression surface and a plurality of translucent sheets are secured to a mounting plate which is mounted over the switchboard, see U.S. Pat. No. 2,818,662. Transparent protective sheets are usually provided to overlay the translucent sheet and protect the recorded indicia.
Simplified erasure means have also been proposed which simplify the erasure operation. Some erasure means comprise slides which can be moved between the translucent sheet and the impression surface to separate the sheet from the surface erasing recorded indicia, see U.S. Pat. No. 4,011,665. Such slide erasure means can be used to control individual translucent sheets independently or adjacent translucent sheets thereby providing independent erasable pads, as illustrated in U.S. Pat. No. 2,894,336. Another form of erasure means is a pneumatically operated system wherein an air blast is used to separate the translucent sheet from the impression surface, see U.S. Pat. Nos. 3,943,643 and 4,051,609. U.S. Pat. Nos. 1,881,140, 2,359,195 and 2,404,563, disclose erasure means in which the impression surface is pulled away from the adhering indicia bearing sheets.
Writing surfaces having easily erasable surfaces are also known. Presently a memo board having a readily erasible surface is marketed by Freelance, Inc., of Willow Grove, Pa. Generally, felt tip pens are used to inscribe these boards with easily erasable indicia.